1. Field of the Invention
The present invention relates to apparatus and to a method for carrying out optical analysis of samples and is applicable in particular to the analysis of biological, chemical and biochemical samples.
2. General Discussion and Related Art
Many chemical, biochemical and biological assays rely upon inducing a change in the optical properties of a biological sample being tested. For example, in order to test for the presence of an antibody in a blood sample, possibly indicating a viral infection, an enzyme-linked immunosorbent assay (ELISA) can be carried out which produces a visible coloured deposit if the antibody is present. An ELISA makes use of a surface which is coated with an antigen specific to the antibody to be tested for. Upon exposure of the surface to the blood sample, antibodies in the sample bind to the antigens. Subsequent staining of the surface with specific enzyme-conjugated antibodies and reaction of the enzyme with a substrate produces a precipitate which shows up the level of antigen binding and hence allows the presence of antibodies in the sample to be identified. This identification is usually carried out using a light microscope which allows an area of the substrate to be viewed by an operator.
In addition to colour staining using an ELISA, techniques such as fluorescence and gold labelling can be used to alter the optical properties of biological antigen material. Similar techniques are also used in general histology to visualise specific areas of tissue, e.g. particular cell types or cell structures, as well as in cell culture.
A significant disadvantage of existing optical analysis techniques is that they are open to human error because of their subjective nature. These techniques are also not suited to uses where a high throughput of samples is required, for example in blood screening applications or cervical smear tests, and are thus relatively expensive to use. The cost factor is exacerbated because, more often than not, different equipment is required for each particular technique.